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CBF 125 Oil Consumption

Blog Date 3 October 2017

The old girl is starting to show her age. At 67,000 miles the CBF125 is looking very tired but then it always has, now her internals must be starting to look tired too.

The corroded aluminium and rusty exhaust of Ren's CBF125
It's no longer a spring chicken these days. 

For all this time I've changed the oil every 2,000 miles. As the miles have rolled by I've slowly become aware that I need to top up the oil every now and then between services. More recently I've noticed I'm having to do this more often and I'm putting in larger quantities of oil.

After the last oil change at 66,000 miles I made a mark on the oil tub, noting the level. Since then I've topped up twice and after 1,300 miles I must have used around 1/2 a litre of oil. These are not accurate measurements but as a rough guide I now consider the oil consumption to be "notable".

The marked level and the current level visible on the side of the oil container
I'm reckoning on half a litre difference give or take.

Bearing in mind that each standard oil change requires *just* over a litre AND the specified service interval is 2,500 miles, it would appear I'm using roughly a litre between recommended changes. As such there seems to be little point in changing the oil, it's running more like a total loss 2-stroke these days! So should I just ignore future oil changes, safe in the knowledge that the oil is always fresh because it's always burning it?

Yes - and no. There's more than one reason to change engine oil. The primary reason to change oil is because the oil degrades but with the regular addition of fresh oil this degradation will be kept in check. However oil also acts as a medium into which dirt and worn metal is suspended. If these are not burnt off then as I continually add fresh oil the concentration of suspended gunk will increase with time.

As such I WILL keep on changing the oil but I'm considering whether or not to move to changing the oil once every 3, 4 or even 5 thousand miles. I'm trying to strike a balance of not just wasting oil by refreshing already refreshed oil against the potential build up of unwanted particles. 

What? Did someone suggest I dismantle the engine and recondition the piston, rings and barrel? How very dare you! That would cost money and I'm not entirely convinced what's left of the CBF125 is really worth it.

Would you like to share your mechanical conundrum? contact ren@bikesandtravels.com

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Reader's Comments

Daf said :-
Though the diminutive CBF is getting on a bit, you've had a bloody good run from it! when the oil consumption gets too ridiculous (or you lose compression and it doesn't run/smoothly) it would be really interesting to see you overhaul the engine/see if it's possible for a home mechanic to do so! Would make a really interesting article series!
04/10/2017 10:37:14 UTC
CrazyFrog said :-
Run it till it drops Ren, it certainly doesn't owe you anything does it?
04/10/2017 12:48:00 UTC
Ren - The Ed said :-
Nah the owd beast has been and still is a good 'un. It owes me nowt and I probably owe it a lot.

Daf - there will be an autopsy. I myself and perhaps quite a few other people would like to see what the internals are like. BUT...but if it's all the same with you I will try and procrastinate that autopsy for as long as possible. I'd like to reach 100,000 miles but I've still got 32,500 miles to go before I get there. Actually I'd like to see 200,000 miles! Actually let's go into lorry distances here, I'd like to see half a million miles.

I don't want to end up with a "Trigger's Brush" situation though. If the motor lets go then that will be that. I'm not thinking of replacing the motor then replacing the fuel pump then replacing the computer then replacing the injector just so I can point at the bike and say "It's done XXX thousand miles that". There are other 125s out there I'd like to destroy - I mean try out.
04/10/2017 12:59:38 UTC
Bob said :-
Is it down on power and / or hard to start?
It might just be stem seals, rather than rings / bore.

My XR125 (23K miles) uses a little oil but it's only the stem seals, it smokes a little on start up but doesn't smoke under normal use and compression is still OK.

That might be the place to start - a compression check.
The other thing would be to see if you're getting oil in the airbox which would indicate blow-by from worn rings.
05/10/2017 10:34:56 UTC
Ren - The Ed said :-
I...I suspect it is down on power although it's not hard to start. If it is down on power it happens over such a long period of time that you don't notice, much like watching your children grow. If I were to ride a much newer CBF125 I may be surprised, much like when a relative who's not seen the kids in a while exclaims "Oh my haven't they grown!"

I'm not seeing any smoke at all, either on startup or general riding. When Sharon was following me the other day she never mentioned a cloud of black soot emanating from my derrière.

The next time I change the spark plug I may do a compression test, I have one of then lying around. I'll also stick my nose into the airbox, I'd not considered looking for oil in there.

Thanks Bob, good calls.
05/10/2017 11:15:28 UTC
ybr125 said :-
Move to a cheap 15w40 oil, it should cut down on the consumpton problem.
05/10/2017 11:51:16 UTC
Ren - The Ed said :-
I'm already running Halford's basic 10w40 motor oil. Are you suggesting the consumption won't be a problem because the oil is cheap or that the thicker cold startup viscosity will reduce consumption?
05/10/2017 12:48:26 UTC
ybr125 said :-
The 15w40 oils are genneraly stronger, thicker, resist shearing better. I would especially recommebd diesel engine oils like Movil Delvac mx 15w40 in your bike. thicker oil should resist consumption much better. 20w50 should also be fine for a tired engine and will give better oil pressure due to larger clearances which developed.
05/10/2017 22:05:24 UTC
Ren - The Ed said :-
I don't know if you are aware but the CBF125's crank is a pressed up needle roller bearing affair. While these are very strong oil choice is critical.

As the needle roller rolls around it forms a ridge of oil in front of each needle. If the oil is too thick the oil ridge won't move out the way fast enough. This apparently causes high pressures and damage. I found this out on a CD200 Benly with noisy tappets. To quieten the tappets as a youth I'd used an oil thickener.

I reckon a 20w50 would be ok but I'm loathe to try at risk of damaging the crank. A 15w40 would be ok as the thickness is the same at running temperature.
06/10/2017 05:57:52 UTC
Jaska said :-
Problem is probably valve stem seal in exhaust valve. That is most likely to cause problems in small high revving engines. Like honda monkey mopeds had same issues a lot.

If seal is not changed in time it might cause the valve to burn which will leave you by the road. And will be more bit more expensive to repair than just changing stem seals.
15/02/2018 18:23:49 UTC
Ren - The Ed said :-
Cheers Jaska. You've got me paranoid now. I was told a long time ago that valve stem seals would usually cause smoke on startup that would clear after being run for a few minutes. That is not the case with my bike. However I am fully open to the notion that my information could be wrong.

I'll look further into this. I can't quite see as yet how a little oil dripping down the valve stem would cause the valve to burn out. Again I need to do my research.

Luckily it is not *too* difficult to change the stem seals on the CBF125 but I am loathe to disturb the motor unless I have good cause too.
16/02/2018 10:04:11 UTC
Ian Soady said :-
In my experience, failing valve seals (particularly inlets) show up by smoking on the overrun as that's when you have a high vacuum in the inlet tract and oil gets sucked in by it.

16/02/2018 10:07:37 UTC
Jaska said :-
There was just in Finnish magazine a long therm 125 test for KTM duke 125 and it burned valve because of valve seal dropped oil on exhaust valve. They only noticed it using oil no smoke or oil smell in exhaust.

Of course it can be something else as well like piston ring etc.

I have CBF125 with similar problem it uses oil almost 1l/1000km and it is bit low on power. Still figuring out whether to to take it apart to replace valve seals and do valve lapping for the bike or sell and buy bigger bike instead.
11/03/2018 20:09:04 UTC
Ren - The Ed said :-
Cheers Jaska.

This is the nightmare of spannering. There is of course the risk that by not sorting out the potential valve stem seal I could cause the demise of the motor. Correspondingly if I strip and "do" the seals then I'll disturb something unnecessarily and equally shorten the motor's lifespan. If it ain't broke then don't fix it.

The 125 continues to use oil but remarkably not as much as it has been. Again the nightmare is pondering what might be going on. Is it the cold weather meaning it's a heat problem? While I'm still using the same Halfords car oil perhaps they've changed something in the mix that's reducing the consumption? Maybe the piston ring gaps all lined up for a while causing the burn but now they've shuffled around and improved the seal? Maybe I've changed my riding style?

In a world of infinite possibilities anything is possible. In the mean time the motor is staying put.
12/03/2018 11:02:05 UTC
Jaska said :-
We have still few months of snow in Finland so my bike is in garage waiting on any decision I make. If I take my bike apart I will tell what I find in here.

I'm usually also if it ain't broken then don't fix it kinda guy but I have no knowledge of the extended history of my bike and for sure I trust my own maintenance skills waay more than 16 years old kids most commonly own 125cc bikes in Finland.
13/03/2018 22:01:34 UTC
Borsuk said :-
Drain your oil out into a clean container when you have a few days when you don't expect to use the bike. Pass it through a filter of some kind, collect the oil and put back in. Might remove some of the major flotsam and crap. Stick a magnet in the filter to remove any ferrous debris that there might be in it. Then you can see if your ferrous bits if any are disintegrating.
13/03/2018 22:47:12 UTC
Ren - The Ed said :-
Borsuk - we're dealing with a 125 here not a 350 tonne ship engine! It won't take a couple of days to filter one litre of oil. Why drain the oil and filter it then put it back in? I usually change my oil every 2,000 miles, as such I have plenty of opportunities to inspect the oil.

I'm not seeing anything untoward in the oil. A while back I ran the used oil through an old rag and didn't see anything of note. I'd be tempted with a magnetic sump plug though.

Jaska - from when until when can you ride in Finland? Here in the UK we get occasional snow that comes and goes. At a rough estimate I'd say there's only about 3 to 7 days a year typically when the snow would stop me riding. We do get a lot of rain though.
14/03/2018 11:00:25 UTC
Borsuk said :-
There's me trying to save you a half litre of oil at oil changes so you don't waste your money, go ahead, be extravagant. :-)
We run ours through centrifugal separators and filters at regular intervals to purify the oil. You could try using a salad spinner.
14/03/2018 11:26:18 UTC
Ren - The Ed said :-
Sorry Borsuk, you're quite right.

I shall be investing in some coffee filter papers, I already have a funnel. Rather than spend good money on a salad spinner I think I shall install 2 half-litre cola bottles onto the wheels of my bicycle. The idea is I'll put one litre of oil into these 2 bottles and pedal like the devil is chasing me. DIY centrifuge.

My question is - how many times do you think I can clean and recycle the oil like this? 3, 4, 5 times or even indefinitely?

Would I be correct in thinking ship oil is not "multigrade"?
14/03/2018 13:13:07 UTC
Borsuk said :-
Actually main engine oil on my ship as far as I know is multi-grade, bog standard 10W 40.

Give me a shout in advance the first time you intend to run your centrifuge bike, I'll make sure I am there with a video camera to directly upload it to Youtube for posterity. In fact I will sell tickets for it if you like, we would make a mint.
14/03/2018 18:37:03 UTC
Ren - The Ed said :-
Has it really reached the stage whereby I have to almost kill myself to become marginally famous and wealthy? I was hoping I could be well known for promoting safe and sensible motorcycling and for taking leisurely travels.

Oh well. I'll let you video my near-death experience Borsuk. I'll also start adding images of semi naked ladies sprawling across exotic yet pointlessly modified motorcycles. I could upload videos of Sharon and I doing wheelies, filtering at 130mph and hitting the rev limiter with no exhaust fitted.

It seems safe, sensible, calm and leisurely doesn't sell.

I'm obviously not serious - but I am aware this website would be a lot lot lot busier and fiscally viable if I did go down the ladies and wheelies route. Sharon! Get yer thong on sweetie we're off fert learn how to crash...I mean wheelie.
15/03/2018 12:57:04 UTC
Jaska said :-
Ren - In middle of Finland where i live snow comes around November-December and it stays until April. 2016 i ended bike season beginning of December and then started riding again first days of April 2017. So time when biking is not really suitable is from 4 to 6 months every year. Today there was 70cm of snow on the back yard. So clearly bike is not my main way of transport i do have car as well.

Of course some people install studded tyres for their bikes and drive all year around. I did that with my moped when i was young and did not have car.
16/03/2018 20:45:47 UTC
Ren - The Ed said :-
I'm feeling cold just reading this Jaska!

This makes me realise just how temperate out climate is here in Britain. We had a round of snow a couple of weeks back, probably about 30cm in the very very worst hit places but in general around 5cm for most. It brought a large part of the country to a halt. Everyone complains that the authorities are useless because the Nordic countries cope but we don't.

We could of course spend millions on ploughs, gritters, studded tyres and snowmobiles only to find we use them 5 days out of every 3,4 or 5 years. Then we'd complain we're wasting money. I imagine you're prepared in Finland because you KNOW it's going to snow.

Studded tyres are not allowed in the UK - probably because we don't get enough snow to warrant them. Have you ever ridden with studded tyres? I've seen them on TV but it is hard to understand how effective they are. Can you ride on ice roads, if so as quick as you can on good tarmac or do you still have to be really careful?
17/03/2018 13:34:24 UTC
Jaska said :-
Ren - Yeah true. Only maybe suitable investment in there would be ploughs that can be installed to tractors front lift. Most of Finnish smaller roads are cleaned with those kind of things as well.

I have ridden Honda Z50J Monkey, and moped scooter with studded tyres both max speed is 45km/h. In those speeds they work ok, of course still very very slippery all the time. So careful yes but if it is hard snow of ice speed can be up to road speeds just need to be really careful on corners and when braking. If there is fresh snow that you need to drive in then bike will be really hard to drive even with proper studded tyres.

In motorcycles there are road legal studded tyres which in fact are quite dangerous things. Basically work only in snow not really in icy conditions. Most people whom drive during winter (that is probably only like 1 % of bikers or so) use heavily studded tyres that are designed for dirt bikes. They work awesome and traction is quite amazing in my understanding. But those tyres dont really work at all on tarmac, so drivers with those tend to use only side roads with snow on the road or gravel roads where it is not so big issue. Dirt bike studded tyres are not of course road legal but most police have common sense that they will not write tickets if those bikes are driven in side roads.

We do have lots of snow, but few days it has been bit warmer and dry so main roads are basically dry tarmac at the moment. But the second you get off the main road there is 5-10 cm of hard snow or ice on the roads.
17/03/2018 21:19:27 UTC
Jaska said :-
One more thing. Studded tyres or high friction winter tyres are mandatory in bikes and cars from start of December until end of February, but of course depending on weather allowed much much longer time. But if you happen to drive with studded tyres during July you will be fined.
17/03/2018 21:24:17 UTC
Ren - The Ed said :-
Cheers Jaska. So studded tyres help a little but they don't make the tyres super wonderful. I've seen the really spikey off road tyres like used on ice speedway, I can see why you can't use them on the main roads!

I guess with the snow and the cold if people use motorcycles for everyday transport they'd have a sidecar or similar?
18/03/2018 12:00:35 UTC
Jaska said :-
Ren - I don't think that anyone uses motorcycles as their primary way of transport during winter. The ones who don't own a car use public transport during winter time.

People who drive during snowy winter are mainly extremist who just really want to ride rather than use the car they still probably have. Because of hard winter motorcycles are mainly a hobby for most people in Finland. Owning proper bike is probalby more expensive than owning decent car in here. Only 125cc bikes are used in many case all year around cause those bikes are mainly used by 16-18 year old that don't have car license yet and only can use those.

Me personally i'm oddity in the sense that i'm 30 and bought 125cc for my first bike even though i have license to drive big bikes as well.
18/03/2018 15:44:45 UTC
Ren - The Ed said :-
Here in the UK it is unusual for a full licence holder like myself to own and run a 125cc motorcycle. I have the best of both worlds, a 125 and a 500.

While the weather here means that motorcycling is possible on almost every day save for the occasional snow storm and high winds, most motorcyclists are "leisure riders". Here too motorcycling is a hobby. Most will avoid the rainy days and the cold winter months.

Times have changed. Motorcycling was a means of transport once upon a time but as wealth has increased and car prices have dropped in relation to earnings it is *almost* as cheap to run a car as it is a larger capacity motorcycle. Running a 125 is still cheap compared to a car though.

Maybe things will change once more. Maybe a fuel shortage. Maybe motorcycles are banned outright for being dangerous. Maybe electric motorcycles turn out to be better or cheaper than electric cars. Who knows.
19/03/2018 12:00:36 UTC

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